There have been fluid sending means (e.g., vortex ring sending apparatuses and air guns) for emitting fluid to any area. Such means include well-known means for applying forced vibration to a molded box to send to a remote area a gas phase obtained with smoke or the like from an opening in the molded box. In such means using forced vibration, forced vibration to be applied to the molded box is achieved by an operation of “hitting” a structure that forms the molded box, the operation being performed mainly by a human.
As regards other means having the same advantages, there are a case where a fan is used for sending and a case where an existing direct drive loudspeaker (speaker) for acoustic radiation intended to radiate an acoustic signal is used (refer to Patent Literature 1, for example). Furthermore, in another case, a solenoid that performs piston oscillation similar to operation of a speaker is used as sending means (the solenoid being configured such that a wire is wound like a coil around a side surface of a cylindrical hollow member and a magnet is disposed in the axis of the cylindrical hollow member) (refer to Patent Literature 2, for example).